<!DOCTYPE html>
<html>
<title>Shared transitions of different elements and shapes</title>
<link rel="help" href="https://github.com/vmpstr/shared-element-transitions">
<link rel="author" href="mailto:vmpstr@chromium.org">

<style>
body {
  background: lightpink;
  overflow: hidden;
}

input {
  position: absolute;
  left: 8px;
  top: 8px;
  z-index: 10;
}

.top {
  top: 0px;
}
.bottom {
  bottom: 0px;
}

div {
  position: absolute;
  left: 0px;
  right: 0px;
  height: 40vh;
  background: green;
  contain: paint;
}
</style>

<input id=toggle type=button value="Toggle!"></input>
<div id=target class=top>
The green div should alternate being at the bottom and at the top.
Other than green and pink background no other colors should appear.
</div>

<script>
let classes = ["top", "bottom"]
let i = 0;
async function runAnimation() {
  await document.documentTransition.prepare({
    rootTransition: "none",
    sharedElements: [target]
  });

  target.classList.remove(classes[i]);
  i = (i + 1) % classes.length;
  target.classList.add(classes[i]);

  await document.documentTransition.start({
    sharedElements: [target]
  });
}

function init() {
  toggle.addEventListener("click", runAnimation);
}
onload = init;
</script>
